1. Field of the Invention
The invention relates to a molding apparatus for lenses, more particularly to a molding apparatus that has individually removable mold cores.
2. Description of the Related Art
Referring to FIG. 1, a currently available molding apparatus for lenses includes a lower mold unit 1 and an upper mold unit 2 facing the lower mold unit 1. The lower mold unit 1 has a lower mold core holder 101, a plurality of lower mold cores 102 disposed within the lower mold core holder 101, and a lower fixed seat 103 to be fixed to a bottom portion of the lower mold core holder 101 so as to retain the lower mold cores 102 in the lower mold core holder 101. The lower mold core holder 101 is formed with a plurality of lower mold core holes 104, each of which has a narrow upper portion and a wider lower portion. Each of the lower mold cores 102 has a shape corresponding to that of a respective one of the lower mold core holes 104. After the lower mold cores 102 are inserted respectively into the lower mold core holes 104, the lower fixed seat 103 is secured to the bottom portion of the lower mold core holder 101 so that the lower mold cores 102 are retained in the lower mold core holes 104.
The upper mold unit 2 has an upper mold core holder 201, a plurality of upper mold cores 202 disposed within the upper mold core holder 201, and an upper fixed seat 203 to be fixed to a top portion of the upper mold core holder 201 so as to retain the upper mold cores 202 in the upper mold core holder 201. The upper mold core holder 201 is formed with a plurality of upper mold core holes 204, each of which has a narrow lower portion and a wider upper portion. Each of the upper mold cores 202 has a shape corresponding to that of a respective one of the upper mold core holes 204. After the upper mold cores 202 are inserted respectively into the upper mold core holes 204, the upper fixed seat 203 is secured to the top portion of the upper mold core holder 201 so that the upper mold cores 202 are retained in the upper mold core holes 204.
Although the aforementioned molding apparatus can achieve its intended purpose, it has the following disadvantages:
1. When inspection of the molded lenses indicates that forming surfaces of some of the lower and upper mold cores 102, 202 are damaged, the defective lower and upper mold cores 102, 202 have to be removed and replaced. To remove the defective lower and upper mold cores 102, 202, the lower and upper fixed seats 103, 203 have to be detached from the bottom and top portions of the lower and upper mold core holders 101, 201, respectively. To remove the lower and upper fixed seats 103, 203 from the lower and upper mold core holders 101, 201, the machine has to be stopped first, and the whole molding apparatus is detached from a machine platform to which the molding apparatus is attached. As such, removal and replacement operations of the defective lower and upper mold cores 102, 202 are not only complicated and time-consuming, but adversely affect the production efficiency as well due to interruption during the molding process.
2. Through the outer diameter tolerance of the lower and upper mold cores 102, 202 that cooperate with the inner diameter tolerance of the lower and upper mold core holes 104, 204 to produce a clearance, the lower and upper mold cores 102, 202 can be easily put in and removed from the lower and upper mold core holes 104, 204. However, due to the presence of the clearances, concentricity problem between the lower and upper mold cores 102, 202 exists, which may result in defective products during the production of the lenses.